8/11/2019 IPTC-14806
1/1
Abstract
One of the key approaches to look for a stratigraphic prospect
in the carbonate reservoir is to map out areas that have
changes
in the rock facies laterally. A workflow of the 2009-2010
exploration study focuses on four key components: Regional new
play concepts, Well log electrofacies, Seismic facies
classification, and Prospect evaluation. This helps to predict
stratigraphic
traps and lithofacies changes within the study area. The
electrofacies analysis calibrated to a reprocessed high resolution
3D
seismic has been carried out in conjunction with Natih and
Shuaiba prospecting concept and analogue fields compilation.
The aim of this integration of well log electrofacies and
Seismic facies is to generate a 3D lithofacies model in the
known
areas where many wells had been drilled, and then use 3D seismic
facies classification to predict lithofacies in the areas where
no wells drilled. Moreover, this integration will provide an
understanding of lateral and vertical facies changes of
reservoirs
and seals within target intervals, which are critical elements
for defining stratigraphic traps.
The electrofacies analysis was carried out by integrating core
data and well log to build a rock type model. This correlation
allows rockfacies to be classified in the cored wells and
predict those facies in the uncored wells. The results of this
electrofacies analysis have demonstrated reservoir property
predictions in terms of porosity and permeability distribution
associated with each rock facies for all wells. On the other
hand, the seismic facies classification was analyzed using
Neural
Network approach based on multiple calibration of seismic
attributes, such as High resolution 3D seismic (AMP), Far
offset
angle stack (FAR), and Acoustic impedance (AI). The first pass
of seismic facies classification was performed without well
data input, so called "unsupervised model". The model will
determine a possibility of seismic facies from all input
attributes,
and generate multiple 3D facies output for both Natih and
Shuaiba Formations.
The most important part of the workflow is the merging between
well log electrofacies and the 3D seismic facies model. The
electrofacies derived from well log provide a detailed specific
rock types at well locations, and the seismic facies would fill
the
gap in the areas without well control. Initially, the seismic
facies were calibrated to the electrofacies rock types at each
well
location, and the prediction was extended laterally throuhout
the area following the defined structural framework. The final
product of this workflow is a "Most Likely" 3D lithofacies
within the target intervals. A 3D probability volume was
alsogenerated to quantify the level of uncertainty, especially in
the areas lacking of well control.
The resulting 3D lithofacies model has reasonably demonstrated
the ability to predict rock facies distribution within the
Natih
and Shuaiba Formations. The output model has provided a key
element to identify prospective areas for stratigraphic traps
within the study area. The 3D lithofacies model based on this
integrated workflow was also useful for the prospect evaluation
and the ranking process of the Natih truncation and Shuaiba
clinoform prospects identified in the exploration study. The
results have confirmed the presence of the Natih-C1 reservoir
and also the predicted rock facies distribution in the upper
part
of Shuaiba Clinoform called shoal anticipated to be good
reservoir quality in each prospect. In addition, the results of
this
work have been utilized for development activities, such as the
updated 2011 3D static and dynamic reservoir models, which
have demonstrated an improvement in terms of production history
matching, reserves determination, and production forecast.
IPTC-14806-PP
Integrated Well Log Electrofacies and Seismic Facies Modeling
forStratigraphic Trap Identification in Carbonate Reservoirs, North
Oman
Author : Patraporn Lertlamnaphakul, PTTEPCo-Authors : Suppakarn
Thanatit, Salam Mahmood Al Busaidi, and Krongpol Seusutthiya
